It looked like Kyle Blanks and Jesus Guzman would be the Padres' primary first basemen after Yonder Alonso injured his right hand in the final game of August. That playing time scenario was indeed the case through the first week of September, but the second week of September has belonged to Tommy Medica. Medica is one of the rare players to lack a RotoWire player profile until hitting the majors, but the Padres appear committed to seeing what he can do with some playing time after hitting 18 home runs at Double-A San Antonio. He was pretty old for the level (age-25 season), but the power has persisted into his first five major league games, and he has already gone yard against legit starters in Cliff Lee and Julio Teheran. Expect him to receive the lion's share of at-bats from first base until Alonso returns (assuming he is able to this season).

Top prospect Matt Davidson was limited to a bit role when he joined the Diamondbacks for a few weeks in August. He has been a bit bigger than that since re-joining the club in the early days of September. Davidson may still be second fiddle to Martin Prado, but Prado's frequent usage in the outfield has allowed Davidson to make consecutive starts twice since his September 3 callup. He has three doubles and one home run in his 21 September at-bats, and the playing time could increase once the Diamondbacks are mathematically eliminated from playoff contention (their not-so-magic number is six). Eric Chavez continues to make infrequent starts against right-handed starting pitchers.

The historically inconsistent Junior Lake surprised most by putting together a relatively steady .295/.333/.428 line through his first 40 games as the Cubs' everyday center fielder. So it was equally surprising to see him lose said center field job when the 28-year-old Ryan Sweeney returned from Triple-A Iowa on September 1. Sweeney has started all but three September games as the Cubs determine whether he will lend a veteran presence to the 2014 club. It does not appear to be a platoon situation since Sweeney has consistently started versus same-handed pitchers. The winds could be changing over these final few weeks, as Sweeney's .205/.311/.410 September may be answering the question as to whether he factors into the Cubs' 2014 outfield in a negative manner.

A month ago, it looked like Kolten Wong's arrival from Triple-A Memphis would introduce a new paradigm to the Cardinals infield, one in which Wong would regularly play second, Matt Carpenter would play third more frequently, and David Freese would meet bench. Wong may be one of the Cardinals' better offensive prospects, but his inability to hit at the major league level caused the aforementioned plan to fall to tatters. He went 3-for-42 through September 4, which won't fly on a St. Louis squad that is scuffling with the Pirates to avoid the Wild Card play-in game. As a result, he has not started in the infield since September 4. Freese has disappointed at the plate for much of the season, but his .362 OBP in September will play.

It looked like Ruben Tejada would be the Mets' shortstop for several years after he ably handled the position in 2011 and 2012 as a 21/22-year-old. However, he earned an extended trip to Triple-A Las Vegas after posting a .529 OPS through the first two months of the 2013 season. He did not return to New York until September 10 after putting up a less-than-stellar .289/.339/.382 in a minor league environment that usually exaggerates offensive stats. However, he had no trouble displacing Omar Quintanilla for the Mets' starting shortstop gig, and he has started all but one game since returning. Tejada has put the ball into play regularly since re-joining the team (he only has one strikeout in 16 plate appearances), but he has had a hard time getting on base (he only has one hit in 16 plate appearances). Still, he should have a virtual monopoly on the position for the Mets' final stretch of games.

As a rule of thumb, it is not a good idea to entrust your second base position to someone the Royals have already expelled. As a rule of another thumb, LASIK surgery should improve your vision at the plate. Both of those thumbs have proven false for the Braves of late. The bottom fell out for Dan Uggla after he returned from LASIK in late August, as he went 4-for-35 (.114) with 12 strikeouts before losing his starting job to Elliot Johnson. Uggla only owns one start over the Braves' last seven games, and there are questions in Atlanta as to whether he will make the Braves' postseason roster. Johnson has not been much better at the plate (.246/.281/.344 since joining the Braves ), but he avoids the strikeout and provides a bit more value with the glove.

The Rangers' left field situation has been a revolving door all season, and that trend has continued into September. Craig Gentry and David Murphy have held down the spot for much of the year (along with Engel Beltre, Leonys Martin, and Jurickson Profar), but roster expansion has introduced the 28-year-old Jim Adduci and 27-year-old Joey Butler. Chances are neither Adduci nor Butler will be a part of the 2014 mix, but they have muddied the waters in September. The starts breakdown in the month has gone: Gentry (five), Murphy (four), Adduci (three), and Butler (one). In other words, owners looking for volume stats over the last two weeks should look elsewhere.

I covered Marcus Semien briefly a few weeks ago in the September callup special, and it looks like manager Robin Ventura is making good on providing the team's best offensive prospect with some at-bats down the stretch. Semien has started the team's last five games, four of which came at third. He has held his own against MLB pitching, and he owns a .421 OBP over those five games. Connor Gillaspie has hastened Semien's rise with uninspiring play at both the plate (his .705 OPS has been near replacement level) and in the field (his 16 errors lead AL third basemen. Jeff Keppinger, who was supposed to serve as the White Sox's starting third baseman this year, has only made one start in September.

A pair of Chrises now own first base in the Twin Cities with Justin Morneau in the playoff hunt with Pittsburgh. Chris Colabello had the spot to himself for the first nine games of the post-Morneau era, but Chris Parmelee arrived and forced a timeshare here after Triple-A Rochester's postseason ended. Parmelee is still only 25 (versus Colabello's 29), but he will need to put together a strong showing over these last two weeks to save his roster spot for 2014. The former prospect has a .226/.311/.366 line between Minnesota and Rochester this season, but he may get some run at first with the latter enduring through a 1-for-18 cold spell.

Derek Jeter's ankle re-injury precipitated a transaction between the Yankees and Mariners that saw Brendan Ryan come to the Bronx. Eduardo Nunez has made a team-high 69 starts at short this season, but he has made zero in the four games since Ryan arrived. Ryan's renowned defense in the middle infield gives him the apparent edge over the semi-incumbent Nunez. The position belongs to these two with Jeter (and Jayson Nix) officially out for the rest of the season, but Nunez could see more time at third base than at short.